[enhancement][DSLX:LSP] Language server could save all "crashes"

### What's hard to do? (limit 100 words)

If there's a XLS_RET_CHECK that happens for some intermediate buffer state it'd be great to have a dump of the language server that caused the internal error to occur.

Because we don't have this, we can encounter transient issues that are hard to recover the input stimulus for.

### Current best alternative workaround (limit 100 words)

Be very careful when making edits or very cognizant of when an internal error happens in the language server.

### Your view of the "best case XLS enhancement" (limit 100 words)

We get something like a flag `--dump_internal_errors_to=/tmp/dir/` where it can dump language server state that exhibits the error and maybe a tool that helps us replay those for reproduction.